Insulating material.



E. W. RICE, JR- INSULATING MATERIAL.

APFLIOATION FILED MAR.15, 1909. RENEWED APR. 19, 1911.

1,049,918 Patented Jan.7, 1913.

WITNESSES! INYENTUR EDWIN W HZLIEZJR ATTLYT UNITED STATES PATENT OFFICE.

EDWIN W. RICE, JR.,

OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, ACORPORATION OF NEW YORK.-

INSULATING MATERIAL.

Patented Jan. '7', 1913.

Application filed March 15, 1909, Serial No. 483,447. Renewed April 19,1911. Serial No. 622,133.

To all whom it may concern:

Be it known that I, EDWIN W. RICE, Jiu, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Insulating Material, ofwhich the following is a specification.

,My invention relates to materials having high insulating qualitieswhich enable them to be used for insulating parts of electricalapparatus having different potentials. The invention is especiallydesigned for insulating the segments of the commutators ofdynamo-electric machines. One of the best known materials is mica, whichhas great mechanical strength and very high insulating andheat-resisting properties, so that it is especially valuable in buildingup commutators; but mica-comes in comparatively thin sheets, and when athick sheet is required it must be built up from several thin ones. Thisbuilding process cannot be carried very far, since the mica varies inthickness and the piling up of a number of sheets produces an'unevennessin gage which is very objectionable. Moreover, the mica does not weardown as fast as the copper segments of the commutator, so that in timethe surface of the commutator becomes rough by reason of the projectingedges of the mica strips, causing the brushes to jump and spark.

The object of my invention is to provide a substitute for the thick micasheets which shall have requisite mechanical strength and flexibilityand high insulating and refractory qualities, can be made of any desiredthickness and of uniform gage, and which will be hard andincompressible, will not shrink, and will wear away as rapidly as thecommutator, so as to preserve a smooth surface thereon.

In the pending application of Gustav A. Dreher, Serial No. 469,767,filed Dec. 29, 1908, there is set forth a process of making aninsulating material composed mainly of kaolin, powdered glass, silko,asbestos and silicate of soda, the resulting compound being a smooth,hard sheet, accurate in thickness and of uniform gage, having highdielectric and heat-resisting properties,'and sufiiciently friable toWear evenly with the copper segments of a commutator when used toinsulate said segments from one another. Owing, however, to the dangerof cracks and holes and to the possibility of minute particles offoreign substances creeping into this compound either during itsmanufacture or by reason of impure raw materials, I have designed thepresent invention to meet this objection.

My invention consists in an insulating sheet composed of two or morethicknesses of the aforesaid compound with interposed sheet or sheets ofmica. The mica may be quite thin, and yet have good mechanical andinsulating properties. Its presence between the layers of the compoundabsolutely preventsany short circuit through the sheet from onecommutator segment to'another due to cracks or other imperfections insaid compound. The. thinness of the mica is such that it readilycrumbles away as rapidly as the compound, and thus no objectionableprojecting" edges are formed when used between commutator segments.

In the accompanying drawing, Figure 1 is a perspective view of a pieceof my improved insulating material, and Fig. 2 shows how it is used inbuilding up a commutator of alternate segments of copper and insulation.

The layers 1 and 2 are composed of the compound hereinbefore referredto, and to which the name of commutite has been given. The thin sheet 3of mica is interposed between the layers of the commutite in the mannerclearly shown in Fig. 1. Strips of this built-up material are placedbetween the copper segments 4 of a commutator, and are adapted toproduce a strong and efficient insulation between said segments, and toWear oif evenly with the copper 1n service.

While the drawing shows but one sheet of mica'placed between two layersof c0mmutite it is evident that this number and arrangement are notessential, but that the number of sheets and layers can be varied andthat their arrangement can be altered to meet the necessities of thecase and I ac-. cordingly do not desire to restrict myself to theparticular arrangement of parts herein shown and described.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,

1. An insulating material for separating parts of electrical apparatushaving different potentials, consisting of layers of commutite and mica.

2. Insulating material consisting of a thin sheet of mica, and a layerof commutite on each side thereof.

3. Acommutator having insulating material between the bars built up oflayers of alternately tough and friable material.

4. A commutator having insulating material between the bars built upwith thin layers of mica and layers of more friable insulating compound.

In witness whereof, I have hereunto set my hand this 9th day of March,1909.

EDWIN W. RICE, JR.

Witnesses BENJAMIN B. HULL, HELEN 'ORFORD,

